Wireless communication systems, such as a mobile phone system, a wireless local area network (WLAN), and the like are widely used nowadays. Also, in the field of wireless communications, in order to further improve communication speed and communication capacity, continuous discussions are being held on next-generation communication techniques. For example, in the 3rd Generation Partnership Project (3GPP), which is a standardization organization, standardization of a communication standard called Long Term Evolution (LTE), and a communication standard called LTE-Advanced (LTE-A), which is based on LTE, has been completed or is being studied.
In such a wireless communication system, a frequency offset or a frequency deviation sometimes occurs by the difference in the clock precision of a base station apparatus (hereinafter referred to as a “base station”) and a terminal apparatus (hereinafter referred to as a “terminal”), and the influence of the Doppler effect of a radio signal. A frequency offset is observed as a phase rotation quantity in a baseband signal. This frequency offset sometimes has a great influence on the reception quality of a reception base station.
As a method of estimating a frequency offset, the following method is provided, for example. That is to say, a method is provided in which a correlation between reference signals received at different timings is calculated so that a phase rotation quantity in a reception interval is estimated.
At the reception base station, it is possible to remove a frequency offset by giving a phase rotation quantity in the opposite direction to the estimated phase rotation quantity to a reception signal, for example. Thereby, it is possible for the base station to obtain a reception signal from which the influence of the frequency offset is reduced.
As a technique for dealing with a frequency offset, the following technique is provided, for example. That is to say, a technique is provided in which a phase difference between reception signals is estimated based on the reference signals received at plurality of different reception intervals. Then in the technique, a phase difference candidate is selected among a plurality of combinations of the phase difference candidates formed by combining phase difference candidates selected for each of the plurality of reception intervals.
With this technique, it is possible to expand a frequency deviation range that is estimable based on a correlation between the reference signals received at different timings, for example. Related technical documents include P. Moose, “A technical for Orthogonal Frequency Division Multiplexing Frequency Offset Correction”, IEEE Trans. Commun., vol. 42, no. 10, October, 1994, and Japanese Laid-open Patent Publication No. 2013-90084, the content of which is incorporated herein by reference in its entirety.